The Salawati basin Irian Jaya is a prolific Basin in Eastern Indonesia, which is producing oil and gas from the Miocene carbonate reservoir, mostly the Kais reef limestone. However, the Matoa Field which is operated by the JOB Pertamina — PetroChina, has two types of the Miocene Kais carbonate reservoir. The reef carbonate (M-20 structure) which has good to excellent reservoir properties and the non reefal (platform) carbonate reservoir which has fair to good porosity and permeability (average porosity 15 — 20 % and average permeability 10 — 30 mD).
The carbonate reef of the Kais Formation in this Matoa field was developed within the platform carbonate without any communication between one and another reservoir types. Both are still producing oil with different method. The reef carbonate reservoir is producing oil by natural flowing, but the platform carbonate reservoir is producing oil by pumping.
Distributions of reservoir properties such as porosity, permeability, net pay thickness or net to gross pay ratio and water cut of each reservoir facies(from the analysis of existing geophysical and geological data on the Matoa field) are clearly different and are important factors to consider for development wells in the Matoa field.
Authors : Raden Idris, Tasiyat & Nana Djumhana